Generative AIs don't remember the original media, they just detect/extract patterns out of them. They aren't able to recreate pixel perfect anything. Ask it to give you a Mona Lisa and the result would just kinda resemble the original. (kinda what a mediocre artist would be able to produce going by their memory)

> I've not heard of any art classes that train you by copying everything that has been produced.

You don't have to learn it, because it's the second nature for humans. We learn by imitation. Babies learn to talk by imitating sounds from parents. Artists learn by imitating style by masters. That's what generative AI does as well.